Frontal airbags are widespread in today's automotive technology. They are the first kind of airbags introduced into the automotive technology and are still key elements of the safety system of a motor vehicle especially of passenger cars. The use of frontal impact airbags saves thousands of lives every year.
Although the present invention can be applied to both, to so-called driver airbags deploying in front of the steering wheel of the motor vehicle as well as to so-called passenger airbags deploying in front of a part of the instrument panel, reference is primary made to passenger airbags since the most relevant application for the current invention are passenger airbags. But it needs to be noted that the invention can also be applied to so-called driver airbags.
The task of a frontal airbag is to protect the head and the thorax of the person sitting in front of this frontal airbag. In case of a “pure” frontal crash (meaning that the vehicle hits another object symmetrically with its front, the deceleration of the car occurs only in the travelling direction of the car (denoted as the X-direction). This is the most often case of a frontal crash and consequently frontal airbags are optimised for this case. In this load case the person hits the impact area of the frontal airbag in a simple linear motion such that no significant lateral forces act between the frontal airbag and the person. The situation changes in the case of a laterally offset frontal crash. This is explained as follows by means of the case in which reference is made to a left-hand driven car.
It happens relatively often that the car hits an object (especially another car driving in the opposite direction) with its front left edge. This leads to a motion of the person(s) sitting in the vehicle to the front and to the left (relative to the vehicle). For the passenger sitting next to the driver, this means that she/he moves forward and to the inside (away from the right side window). A typical angle of movement is 20°. This can lead to the following: when the head of the passenger hits the impact area of the frontal airbag the head is held by the same because of frictional forces, but the body of the passenger continues to move towards the inside of the car. This can lead to a very quick rotation of the head and/or to high forces in the neck of the passenger. Both can have negative consequences.
It is the task of the invention to provide a frontal airbag for providing improved protection of the person to be protected during a laterally offset frontal crash.
This task is solved by a frontal airbag a module with such a frontal airbag, and a vehicle with such a module as described herein.
A feature of the present invention is to provide a first tether which is connected to the impact area of the outer skin of the frontal airbag along two connections which are spaced from each other in the transverse direction of the vehicle (referred to as the first direction). This first tether and the two connections preferably extend along a substantial part of the height of the impact area such that a section of the impact area (referred to as the intermediate section) is spanned over by this first tether. This first tether is under tension when the airbag is fully deployed because the first tether is (in the first direction) shorter than the intermediate section and/or because the presence of a second tether connecting the first tether to another part of the airbag or to the housing of the airbag module. Due to the tension in the first tether, the tension in the section of the frontal airbag which is spanned over by the first tether (the intermediate section) is reduced at least in the first direction, such that a “soft cell” is created which allows a movement of the head in the first direction after the head hit the impact area. This leads to less rotational forces on the head and to lower forces applied to the neck.
Since in the case of a laterally offset crash the head usually hits the impact area offset of its center, the intermediate section (soft cell) is preferably also offset from the center.
In order to ensure that the impact area, or a part of the same “follows” the passenger along a substantial time of restraining process, it can be further preferred that the whole airbag is able to rotate in the horizontal plane along its connection to the housing.